SOLUTION: Please help me solve this question. A motorist travelled 20km of an average speed of 15km/h. If he made the return journey at an average speed of 30km/h,find the average speed o

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Question 1118275: Please help me solve this question.
A motorist travelled 20km of an average speed of 15km/h. If he made the return journey at an average speed of 30km/h,find the average speed of the whole journey.
Thank you
Answer by josgarithmetic(39625) About Me  (Show Source):
You can put this solution on YOUR website!
                SPEED        TIME       DISTANCE
GOING            15          20/15        20
RETURN           30          20/30        20
TOTAL                        t            d=40


Whole-trip average speed is d%2Ft=40%2F%2820%2F15%2B20%2F30%29
-
40%2F%2820%281%2F15%2B1%2F30%29%29
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2%2F%282%2F30%2B1%2F30%29

2%2F%283%2F30%29

2%2F%281%2F10%29

highlight%2820%29